Information carrier comprising access information

ABSTRACT

An apparatus for accessing an information carrier for holding user information includes access information for accessing the user information, the access information being stored in a pre-determined first region on the information carrier. The information carrier further includes at least one further region different from the first region, the further region comprising dummy information.

This application is a continuation of prior U.S. patent application Ser.No. 13/352,370, filed Jan. 18, 2012, which is a continuation of priorU.S. patent application Ser. No. 13/004,126, filed Jan. 11, 2011, whichis a continuation of prior U.S. patent application Ser. No. 10/545,637,filed Aug. 16, 2005, which is a National Stage Application ofPCT/IB2004/050087 and which claims the benefit of Dutch PatentApplication No. 1022741, filed Feb. 20, 2001, the entire contents ofeach of which are incorporated herein by reference thereto.

The invention relates to an information carrier for holding userinformation, information carrier comprising access information foraccessing the user information, the access information being stored in apre-determined first region on the information carrier. The inventionfurther relates to an apparatus for reading out information from theinformation carrier.

The art of hiding access information on an information carrier forholding user information is laid in the fact that you distract peoples'(the hackers) attention from the access information that you want tohide. Using this access information, the user information on theinformation carrier can be accessed. For copy protection purposes it issometimes desired to hide this access information; this accessinformation can for example be hidden in the user information you wantto protect or this access information can be hidden in a side channelpresent on the information carrier. From optical information carrierssuch as CD or DVD, it is for example known that this access informationcan be written in a so-called “wobble channel” (sometimes also called“radial error channel”).

It is an object of the invention to realize an information carriercomprising access information for which illegal retrieval of the userinformation is further prevented.

According to the invention, this object is achieved by the informationcarrier which is characterized in that the information carrier furthercomprises at least one further region different from the first region,the further region comprising dummy information stored on theinformation carrier.

The invention is based on an insight that the noise level of the readout signal increases somewhat in the region(s) where the accessinformation is hidden. Malicious people can observe this noise level anddetermine the region where the access information is located. Using theposition of this region can be used in further attempts to illegallyretrieve the access information. To avoid this difference in noise levelbetween regions with and without the access information, this accessinformation is assigned for only a specific region of the informationcarrier, but dummy information is also written in other regions. Thisinformation is called dummy information as it comprises no informationabout the access information. By observing the signals from theinformation carrier no difference between access or dummy informationcan be noticed, as only pre-knowledge about the exact position of theaccess information enables the possibility of retrieving this accessinformation. Due to this, an improved copy protection system againstillegal read Gut of the user information present or to be present on theinformation carrier is realized.

In an embodiment of the information carrier according the invention,wherein the access information is stored on the information carrieraccording to a pre-determined format, the information carrier ischaracterized in that the dummy information is stored on the informationcarrier according to the same or similar format. With the term “format”is indicated that the way in which the information, in this case theaccess information and the user information are stored on theinformation. Every information must be converted according to a certainformat in order to make it suitable for recording on an informationcarrier. The dummy information is stored on the information carrieraccording to the same or similar format as used for the accessinformation as the change in the noise level of the read out signal forthe dummy information will in that case be similar to the change in thenoise level of the read out signal for the access information. This hasthe advantage that determining the exact position of the accessinformation is made more difficult.

In another embodiment of the information carrier according to theinvention, the information carrier is characterized in that thepre-determined first region is a region which is accessed by anapparatus for playing and/or recording the information carrier when itinitially access the information carrier. It is important for theintegrity of the access information that the number of people knowingabout the position on the information carrier of the access informationmust be kept as limited as possible. However, pre-knowledge about theexact position of the access information is necessary to retrieve it. Toprevent disclosing this information about the position detection tosemiconductor companies that make IC's to be used in an apparatus forplaying the information carrier according to the invention, the positionof the access information can be supplied to them by a piece of VERILOGcode, with a well defined interface, which can be added to their own ICdesign and takes care of the detection of the access information, inthis way semiconductor companies do not need to be informed about theexact position of the access information. It is advantageous not havingto inform the drive designing companies to design the drive such that itfirst has to access this exact position for a certain time and thenproceed with the normal procedure again, as this might reveal theposition of the access information. In order to be able to keep theposition of the access information a secret, the pre-determined firstregion comprising the access information is a region which is accessedby the apparatus for playing and/or recording the information carrierwhen it initially access the information carrier. Thus, by taking carethat the access information is written in a region where the playbackdevice has to be anyway when it initially accesses the informationcarrier, the access information can be read without informing the IC ordrive manufacturers. This has as a further advantage that the positionof the access information does not have to be mentioned in the standardspecification describing the information carrier according to theinvention. This position information only remains in the VERILOG code.Types of regions that can be used for this are for example: the TOC(table of contents) region, the DI (disc information) region, the MKB(Media Key Block) region or another place where other access or copycontrol information is stored.

In another embodiment of the information carrier according to theinvention, the information carrier is characterized in that theinformation carrier comprises the user information, the accessinformation being buried in the user information, By burying the accessinformation in the user information, tampering with the accessinformation is discouraged, as amending (part of) the access informationcan result in unintentional removal or damage of the user information.Several techniques for burying data are known in the art, for examplefrom Principles of Digital Audio, Ken C. Pohlmann, fourth edition, 2000,pages 678-680. In these techniques dithering and noise shaping isapplied to a data signal for enabling replacing severalleast-significant bits with buried data.

In another embodiment of the information carrier according to theinvention, the information carrier is characterized in that the accessinformation is stored in a side channel of the information carrier. Bystored the access information in a side channel retrieving thisinformation is further hindered. Side channels which can for example beused for this are: a “wobble channel” in which the information is storedin the modulation of the radial position of the pits/marks in a wobbledtrack, as is used for example in the CD-R and CD-RW discs; a “wobblechannel” in which the information is stored in the modulation of thetangential position of the pits/marks in a wobbled track, for example bytime base modulation, or pit shift; a side channel which is created bymodulating the pit shape, as for example used in so-called LimitedMultilevel techniques, as is described in International PatentApplication WO 00/57416 A1 (PHN 17.369); this pit shape can be modulatedin different ways, for example by modulation of the pit-depth orpit-with, but also by creating pear-shaped pits, or dog-bone shapesbits; a side channel which is created by using special bit-strings. Inprinciple every deviation from a physical parameter which results in adetectable analog signal can be used for creating an analog sidechannel. The channel modulation can also be used for introducing adigital side channel.

In another embodiment, the information carrier further comprises aPermanent Information & Control data (PIC) zone, the access informationbeing stored in the PIC zone. In this PIC zone, general informationabout the information carrier and various other information are stored.This so-called PIC information can be stored in pre-recorded pits/lands(or marks/lands), but this information can also be stored inpre-recorded high frequency modulated (HFM) grooves which are modulatedin the radial direction with a rather high bandwidth signal. This PICzone is used in a new optical information carrier, called BluRay disc,In another embodiment, the information carrier is a read-only opticalinformation carrier, like for example a DVD-ROM disc or a BluRay-ROMdisc. The access information can for example be stored in apre-determined region of the PIC zone and the dummy information can bestored in other regions of the PIC zone.

In another embodiment, the position of the pre-determined first regionis hidden on the information carrier. This position can for example, inthe case of an information carrier comprising a wobbled pre-groove, behidden in the radial excursion of the wobbled pre-groove.

In another embodiment, the information carrier further comprises aspecial area comprising position bits indicating the position of thepre-determined first region. The position bits can for example be storedon the information carrier in a variation of a parameter, whichvariation is detectable by integration detection. For example in thecase of an information carrier comprising a PIC zone, a reference to theposition of the access information in the PIC zone is stored on theinformation carrier. In the PIC zone, a main data channel with AddressUnit Numbers (AUN) is present. These AUNs are used for indicating thestarting position of the access information in the PIC zone. In order tohinder the illegal retrieval of the access information, methods exist tohide the access information into the noise of this channel. For examplespread spectrum techniques can be used for this. In these techniques,the hidden access information can be detected by integrating the readout signal in a special way. Spread spectrum techniques are for exampleknown from “Digital Modulation and Coding”, Wilson. p. 247-256 and thereferences therein. Integration detection is for example known from“Digital Baseband Transmission and Recording”, Jan W. M. Bergmans, p.122-129. In spread spectrum techniques the bandwidth of a signal isintentionally made larger using spread spectrum modulation. Themodulated signal can be detected using integration detecting methodsusing for example a hypothetical maximum-likelihood receiver.

The invention further relates to an apparatus for reading outinformation from the information carrier according to the invention, theapparatus comprises a reading unit for reading out user information andaccess information from the information carrier, and access controlmeans for providing access to the user information in dependence on theaccess information.

These and other aspects of the invention are apparent from and will beelucidated with reference to the embodiments described hereinafter. inthe drawings:

FIG. 1 shows a first embodiment of the information carrier according tothe invention,

FIG. 2 shows a second embodiment of the information carrier according tothe invention, in which the access information and the dummy informationare stored in the PIC zone,

FIG. 3 shows a third embodiment of the information carrier according tothe invention, in which the exact location of the access information inthe PIC zone is indicated,

FIG. 4 shows an embodiment of an apparatus for reading out accessinformation from an information carrier,

FIG. 5 shows an embodiment of the use of the access information forgiving access to the user information.

In FIG. 1 a first embodiment of the information carrier according to theinvention is shown. Information carrier 1 exhibits a track patterncomprising a spiral groove 2 of constant width provided with a radialwobble. These teachings are, among others, used in the well-knownstandardized CD--R discs. For the sake of clarity the pitch of thespiral and the radial wobble are strongly exaggerated. In general, thepitch of the consecutive turns of the spiral path is generally of theorder of magnitude of 1 to 2 μm. In this Figure, two possibleembodiments of this information in which the access information isstored in a wobble channel are shown, as an enlargement of box 3. inthese implementations the information on the physical parameter isstored in the lead-in of the information carrier. The lead-in of theinformation carrier is an area on the information carrier situatedbefore the area comprising the user information. Track 1.1 shows thegroove in which the access information is stored as a width variation ofthe track. This variation has a certain length, indicated with thereference number 4. The information can be read out from the recordcarrier using the tracking signals available in a standard device forreading out record carriers, e.g. a CD or DVD player. Track 1.2 shows atrack in which the access information is stored as in the form of adeviation of the track from the average centerline 5. Such a deviatingtrack, which is generally called a wobble, is used in differentstandardized optical record carriers, like e.g. the CD-R disc and theDVD+RW disc. Additional information can be found in U.S. Pat. No.4,972,401 (=PHN 9666).

In this embodiment, in the lead-in both a pre-determined region forholding the access information and a further region for holding dummyinformation are defined. This access information can for example be usedfor decrypting the user information stored on the information carrier.

Another embodiment is shown in FIG. 2, in which the access informationand the dummy information are stored in the PIC zone of the informationcarrier. In this embodiment, the information carrier comprises aso-called Permanent Information & Control data (PIC) zone. In this PICzone general information about the information carrier and various otherinformation in stored. In this way, a data channel for pre-recordedinformation with sufficient capacity and data rate is created. In thisembodiment, the PIC information is stored in pre-recorded pits/lands (ormarks/lands), but this information can also be stored in pre-recordedhigh frequency modulated (HFM) grooves which are modulated in the radialdirection with a rather high bandwidth signal. Due to the fact that theinformation is stored in a wobble channel, a buried channel is created.In FIG. 2 the layout of the information carrier comprising the PIC zoneis indicated. The area on the information carrier nearest to the carriercenter is called the Inner area (IA) 6. Next to this is the Clampingarea (CA) 7 which is used by the playing apparatus for clamping theinformation carrier so that a stable rotation can be accomplished. Nextto this is the Transition area (TA) 8. After this area, the Informationarea (IA) is situated. This Information area comprises the InformationZone (IZ) and the Burst Cutting Area (BCA) 9. The Burst Cutting Area isused to add information to the information carrier after completion ofthe manufacturing process. The BCA-code can be written by a high-powerlaser system or by the initializes in case of rewritable discs. TheInformation Zone (IZ) comprises the Lead-in Zone (LI), the Data Area 12and the Lead-out Zone (LO) 13. The Lead-in Zone comprises the PIC zone10 and the rest of the Lead-in Zone 11.

In this embodiment, the access information is stored in a pre-determinedregion of the PIC zone; the other regions of the PIC zone comprise thedummy information. This dummy information is written in the same formatas the access information.

In order to be able to read out the access information, a reference tothe position of the access information in the PIC zone can be retrievedby a certain method. In this embodiment this method is as follows. ThePIC zone comprises a main data channel, with Address Unit Numbers (AUN).These AUN are used for indicating the starting position of the accessinformation in the PIC zone. This is possible as the wobble channelsignal is locked to the data signal (HF-channel). An address is 4 bytes(without ECC bytes). As the PIC zone is only situated in a small part ofthe information carrier, only a limited number of the least significantbits (lsb's) of the 32 bits change within the PIC zone (generally onlythe first 16 lsb's). These 16 bits are sufficient to determine theposition within the PIC zone. The

PIC zone extends over some 2000 tracks; suppose that the accessinformation is only present in 20 consecutive tracks, the startingposition of this access information being determined by an AUN from theuser information. The first 16 lsb's of this AUN are than positionedover the complete PIC zone, for example using an unscrambled modulation.Due to that, it becomes possible, when you arrive at a random positionin the PIC zone, to read out the first 16 bits of the AUN, to jump tothe starting position of the access information, and to read out theaccess information. In this way, the exact location of the accessinformation is further hidden in the PIC zone, as it is only situated ina certain position in this band, and not throughout the complete band.

Another embodiment of the information carrier according to theinvention, in which the exact location of the access information in thePIC zone is indicated is shown in FIG. 3 in this embodiment theinformation carrier comprises four Key frames 14. In these Key frames,31 sync frames are present, being numbered from 0 to 30. In sync framesnumber 3, 7, 11, 15, 19, 23 and 27 (indicated with reference number 15)an 8-bit number is stored which indicates the exact location of theaccess information. In the case the access information accessinformation is stored on the information carrier in a variation of aparameter, which variation is detectable by integration detection, theexact location of the access information can be changed using this 8 bitnumber. This 8-bit number can than for example indicate which seed andpermutation should be used for detecting the bits making up the accessinformation.

FIG. 4 shows an embodiment of an apparatus for reading out accessinformation from an information carrier. The apparatus comprises areading unit for reading out user information and access informationfrom the record carrier 1. The read unit comprises a read head 41 forscanning the track and generating a read signal corresponding to thephysical marks on the record carrier, and a translating unit 42 fortranslating the read signal into the bit sequence, e.g. an EFM decoderfor decoding in a CD system. The bit sequence is coupled to anerror-correcting unit 43 for recovering the information and correctingpossible errors, e.g. the CIRC corrector in a CD system. The recoveredinformation is coupled to access control means 17 for controlling theaccess to the information. The read out access information is availablefor further processing on the output 48 of the access control means 47.During reading the read head 41 is positioned on the track by a servounit 44 of the usual type, while the record carrier is rotated by amotor unit 45. The reading of information is controlled via a controller46, which controller controls the motor unit 45, the servo unit 44 andthe error correction unit 43, and is arranged for receiving readcommands, e.g. via an interface to the access control means 47.

The reading out of the access information will be effected as follows.The access control means will read out the pre-determined first regioncomprising the access information, e.g. PIC zone. Using this accessinformation, which can for example be a decryption key for decryptingthe encrypted user information, access is given to the user information.In the case the information carrier does not comprise the accessinformation, or the apparatus is not capable of reading out the accessinformation, the information carrier will be rejected and access to theuser information will be barred.

FIG. 5 shows an embodiment of the use of the access information forgiving access to the user information. It is shown that user information16 is read out from the information carrier 1, for example using theapparatus as shown in FIG. 4. The access information 17 is detected in adetection module 18. The detection module has knowledge on the exactlocation of the access information, or the detection module is able todetect this location as it is familiar where position bits indicatingthe position of the access information are present on the informationcarrier. These position bits can for example be detected usingintegration detection. Using this detected access information thedecryption key is calculated in module 19. As an extra input for thiscalculation a random number 20 is used. This number can be a numberhidden on the information carrier, but can also be inputted by the userof the apparatus. The calculated key is used in decryption module 21 todecrypt the user information. After decryption of the user informationthis information is further processed or outputted. This can be madeconditional on the detection of the correct access information. Modules18, 19 and 21 can be supplied to the IC manufacturers in VERILOG code.Due to this, no information on the access information detection or thekey calculation have to be disclosed, as this takes places inside theVERILOG block 22.

Although the invention has been elucidated with reference to theembodiments described above, it will be evident that other embodimentsmay be alternatively used to achieve the same object. The scope of theinvention is therefore not limited to the embodiments described above,but can also be applied to all kinds of information carriers, read-only,write-once or rewritable types of carriers. The scope of the inventionis further not limited to certain kinds of access information. Allinformation which is or can be used as access information, i.e.information used for giving access to the user information stored or tobe stored on the information carrier according to the invention fallwithin the scope of the invention. The scope of the invention is furthernot limited to certain buried channel techniques or certain (hidden)side channels. All techniques and channels which can be used for storinginformation fall within the scope of the invention.

It must further be noted that the term “comprises/comprising” when usedin this specification, including the claims, is taken to specify thepresence of stated features, integers, steps or components, but does notexclude the presence or addition of one or more other features,integers, steps, components or groups thereof. It must also be notedthat the word “a” or an preceding an element in a claim does not excludethe presence of a plurality of such elements. Moreover, any referencesigns do not limit the scope of the claims; the invention can beimplemented by means of both hardware and software, and several “means”may be represented by the same item of hardware. Furthermore, theinvention resides in each and every novel feature or combination offeatures.

The invention can be summarized as follows: the invention relates to aninformation carrier for holding user information, the informationcarrier comprising access information for accessing the userinformation, the access information being stored in a pre-first regionon the information carrier. The information carrier further comprises atleast one further region different from the first region, the furtherregion comprising dummy information. The invention is based on theinsight that the noise level of a read out signal increases somewhat inthe region(s) where the access information is hidden. To avoid thisdifference in noise level between regions with and without the accessinformation, this access information is assigned for only a specificregion of the information carrier, but dummy information is also writtenin other regions. Due to this, an improved copy protection systemagainst illegal read out of the user information present or to bepresent on the information carrier is realized.

1. An apparatus for reading out information from an information carrier,the apparatus comprising: a reading unit configured to read out userinformation and access information from the information carrier; andaccess control unit configured to provide access to the user informationin dependence on the access information; wherein the access informationare stored in a pre-determined first region on information carrier, andwherein dummy information are stored in at least one further region, andwherein a change in a noise level of a read out signal for the dummyinformation is similar to a change of a noise level of a read out signalfor the access information.
 2. The apparatus of claim 1, whereinapparatus is configured to initially accesses the predetermined firstregion when reading the information carrier.
 3. The apparatus of claim1, wherein the predetermined first region is the Table of Contentsregion, the Disc Information region or the Media Key Block region. 4.The apparatus of claim 1, wherein the information carrier furthercomprises a Permanent Information and Control data (PIC) zone, theaccess information being stored in the PIC zone.
 5. The apparatus ofclaim 4, wherein the access information is stored in the PIC zonepre-recorded pits-lands or in pre-recorded high frequency modulatedgrooves.
 6. The apparatus of claim 4, wherein the access information isstored in a pre-determined region of the PIC zone, the dummy informationbeing stored in other regions of the PIC zone.
 7. The apparatus of claim1, wherein the information c r comprises a read-only optical informationcarrier.
 8. The apparatus of claim 1, wherein a position of thepre-determined first region is hidden on the information carrier.
 9. Theapparatus of claim 8, wherein the information carrier further comprisesa special area comprising position bits indicating the position of thepre-determined first region.
 10. The apparatus of claim 1, wherein theaccess information is stored on the information carrier in a variationof a parameter, the parameter being a radial position of pits-marks in awobbled track.
 11. The apparatus of claim 10, wherein the variation ofthe parameter is detectable by integration detection.
 12. The apparatusof claim 1, further comprising a detection module configured to detectthe access information in the pre-determined first region by integrationdetection.
 13. The apparatus of claim 1, further comprising a detectionmodule configured to detect position bits indicating a position of thepre-determined first region.
 14. The apparatus of claim 13, wherein theposition bits are stored in a special area of the information carriercomprising position bits indicating a position of the pre-determinedfirst region.
 15. The apparatus of claim 14, wherein the position bitsare stored on the information carrier in a variation of a parameter, andwherein the variation is detectable by integration detection.
 16. Theapparatus of claim 1, further comprising a detection module configuredto detect the access information in the pre-determined first region,wherein the access control unit and the detection module are integratedinto a VERILOG block.
 17. The apparatus of claim 1, wherein the dummyinformation is stored on the information carrier according to a same orsimilar format as used for the access information, so that a change inthe noise level of a read out signal for the dummy information issimilar to a change in the noise level of a read out signal for theaccess information.
 18. The apparatus of claim 1, wherein the accessinformation is stored on the information carrier in a side channel, theside channel being a wobbled pre-groove or a wobbled information track.19. The apparatus of claim 1 wherein a position of the first region ishidden in a radial excursion of a wobbled pre-groove or a wobbledinformation track of the information carrier.
 20. The apparatus of claim1, wherein the first region and the second region are in a lead-in areaof the information carrier situated before a user region comprising theuser information.
 21. The apparatus of claim 1, wherein the informationcarrier further comprises position information related to a position ofthe access information stored in portions of sync frames included in theinformation carrier.
 22. The apparatus of claim 21, wherein the positioninformation are included in every fourth sync frames of key framesincluded in the information carrier.
 23. The apparatus of claim 1,wherein the access control unit is further configured to calculate adecryption key using the access information, and to decrypt the userinformation using the decryption key.
 24. The apparatus of claim 23,wherein the access control unit is further configured to hide a randomnumber for use in calculating the decryption key.
 25. The apparatus ofclaim 1, wherein the access control unit is further configured to burythe access information in the user information.
 26. A non-transitorycomputer readable media for insertion into a reading apparatus forreading user information from the media; the media comprising: a firstregion comprising access control information and a different furtherregion comprising dummy information, wherein a change in a noise levelof a read out signal for the dummy information is similar to a change ofa noise level of a read out signal for the access information; and userinformation, wherein the access control information is configured tocontrol a controller of the reading apparatus to provide access to theuser information depending on the access information.
 27. The media ofclaim 26, wherein a position of the first region is predetermined by astandard for the media.
 28. The media of claim 26, wherein the accessinformation is stored on the information carrier in a side channel, theside channel being a wobbled pre-groove or a wobbled information track.29. The media of claim 26, wherein the access information is stored onthe media as encoded deviations in a lateral position of a wobbledpre-groove or a wobbled information track.
 30. The media o claim 26,wherein the dummy information is stored on the information carrieraccording to a he same or similar format as used for the accessinformation, so that the change in the noise level of the read outsignal for the dummy information is similar to the change in the noiselevel of the read out signal for the access information.